It is important that ribbons, which are used in the technical field, in particular with vehicle safety belts, remain dimensionally stable in use.
Vehicle safety belts which are continually abraded by the user in running over the deflection pulley and the socket tongue tend to deform, in particular when they are produced on modern needle weaving looms and thus have uneven edges (weft entry side=selvedge, weft exit side=crochet edge).
Wavy or sabre-like deformed belt webbing can no longer be neatly coiled with the common automatic seat belt retractors and there is the risk that in a crash situation the vehicle occupant with his/her seat belt fastened is displaced too far forwards due to the thus occurring “belt slack” with an enormous added risk of injury.
In the production of vehicle safety belts, particular attention must be paid to good abrasive properties. During the weaving process already, the yarn tension should be uniform over the entire bandwidth from edge to edge.
Above all, both edge regions must have the same properties.
This is very difficult to put into practice, especially with ribbons woven on modern needle weaving looms due to the different edge designs on account of the weaving technique (weft entry side=selvedge, weft exit side=crochet edge).
The thus produced ribbons deform frequently and become wavy or sabre-curved.
Identical edges in terms of weaving are only achieved with pick-and-pick (shuttle) weaving looms. On needle weaving looms, two alternating picks working in opposite directions have to be used, cf. e.g., DE 102 28 066 B4, in order to achieve identical edges in terms of weaving.
This method comprises crocheting the weft loops with so-called auxiliary or catch yarns. The crocheting can be released in the finished woven fabric when the auxiliary yarn is damaged (run effect) if an additional blocking yarn does not secure it.
Thus, this weaving method is complicated and difficult to adjust due to the auxiliary and blocking yarns feeder difficult to adjust. Moreover, both yarns have to be delivered to the weaving spot by a positive yarn transport.